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ADD COLUMN is a subcommand of ALTER TABLE. Use ADD COLUMN to add columns to existing tables.
Note:
The ADD COLUMN statement performs a schema change. For more information about how online schema changes work in CockroachDB, see Online Schema Changes.
Tip:
This command can be combined with other ALTER TABLE commands in a single statement. For a list of commands that can be combined, see ALTER TABLE. For a demonstration, see Add and rename columns atomically.
Synopsis
Required privileges
The user must have the CREATE privilege on the table.
Parameters
| Parameter | Description |
|---|---|
table_name |
The name of the table to which you want to add the column. |
column_name |
The name of the column you want to add. The column name must follow these identifier rules and must be unique within the table but can have the same name as indexes or constraints. |
typename |
The data type of the new column. |
col_qualification |
An optional list of column qualifications. |
Viewing schema changes
This schema change statement is registered as a job. You can view long-running jobs with SHOW JOBS.
Examples
Setup
The following examples use the bank demo database schema.
To follow along, run cockroach demo bank to start a temporary, in-memory cluster with the bank schema and dataset preloaded:
$ cockroach demo bank
Add a single column
> ALTER TABLE bank ADD COLUMN active BOOL;
> SHOW COLUMNS FROM bank;
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden
--------------+-----------+-------------+----------------+-----------------------+-------------+------------
id | INT8 | false | NULL | | {bank_pkey} | false
balance | INT8 | true | NULL | | {bank_pkey} | false
payload | STRING | true | NULL | | {bank_pkey} | false
active | BOOL | true | NULL | | {bank_pkey} | false
(4 rows)
Add multiple columns
> ALTER TABLE bank ADD COLUMN location STRING, ADD COLUMN currency STRING;
> SHOW COLUMNS FROM bank;
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden
--------------+-----------+-------------+----------------+-----------------------+-------------+------------
id | INT8 | false | NULL | | {bank_pkey} | false
balance | INT8 | true | NULL | | {bank_pkey} | false
payload | STRING | true | NULL | | {bank_pkey} | false
active | BOOL | true | NULL | | {bank_pkey} | false
location | STRING | true | NULL | | {bank_pkey} | false
currency | STRING | true | NULL | | {bank_pkey} | false
(6 rows)
Add a column with a NOT NULL constraint and a DEFAULT value
> ALTER TABLE bank ADD COLUMN interest DECIMAL NOT NULL DEFAULT (DECIMAL '1.3');
> SHOW COLUMNS FROM bank;
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden
--------------+-----------+-------------+------------------------+-----------------------+-------------+------------
id | INT8 | false | NULL | | {bank_pkey} | false
balance | INT8 | true | NULL | | {bank_pkey} | false
payload | STRING | true | NULL | | {bank_pkey} | false
active | BOOL | true | NULL | | {bank_pkey} | false
location | STRING | true | NULL | | {bank_pkey} | false
currency | STRING | true | NULL | | {bank_pkey} | false
interest | DECIMAL | false | 1.3:::DECIMAL::DECIMAL | | {bank_pkey} | false
(7 rows)
Add a column with a UNIQUE constraint
> ALTER TABLE bank ADD COLUMN address STRING UNIQUE;
> SHOW COLUMNS FROM bank;
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden
--------------+-----------+-------------+----------------+-----------------------+------------------------------+------------
id | INT8 | false | NULL | | {bank_address_key,bank_pkey} | false
balance | INT8 | true | NULL | | {bank_pkey} | false
payload | STRING | true | NULL | | {bank_pkey} | false
active | BOOL | true | NULL | | {bank_pkey} | false
location | STRING | true | NULL | | {bank_pkey} | false
currency | STRING | true | NULL | | {bank_pkey} | false
interest | DECIMAL | false | 1.3:::DECIMAL | | {bank_pkey} | false
address | STRING | true | NULL | | {bank_address_key,bank_pkey} | false
(8 rows)
Add a column with a FOREIGN KEY constraint
> CREATE TABLE customers (
id INT PRIMARY KEY,
name STRING
);
> ALTER TABLE bank ADD COLUMN cust_number INT REFERENCES customers(id);
> SHOW COLUMNS FROM bank;
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden
--------------+-----------+-------------+----------------+-----------------------+------------------------------+------------
id | INT8 | false | NULL | | {bank_address_key,bank_pkey} | false
balance | INT8 | true | NULL | | {bank_pkey} | false
payload | STRING | true | NULL | | {bank_pkey} | false
active | BOOL | true | NULL | | {bank_pkey} | false
location | STRING | true | NULL | | {bank_pkey} | false
currency | STRING | true | NULL | | {bank_pkey} | false
interest | DECIMAL | false | 1.3:::DECIMAL | | {bank_pkey} | false
address | STRING | true | NULL | | {bank_address_key,bank_pkey} | false
cust_number | INT8 | true | NULL | | {bank_pkey} | false
(9 rows)
> SHOW CONSTRAINTS FROM bank;
table_name | constraint_name | constraint_type | details | validated
-------------+-----------------------+-----------------+----------------------------------------------------+------------
bank | bank_address_key | UNIQUE | UNIQUE (address ASC) | t
bank | bank_cust_number_fkey | FOREIGN KEY | FOREIGN KEY (cust_number) REFERENCES customers(id) | t
bank | bank_pkey | PRIMARY KEY | PRIMARY KEY (id ASC) | t
(3 rows)
Add a column with collation
> ALTER TABLE bank ADD COLUMN more_names STRING COLLATE en;
> SHOW COLUMNS FROM bank;
column_name | data_type | is_nullable | column_default | generation_expression | indices | is_hidden
--------------+-------------------+-------------+----------------+-----------------------+------------------------------+------------
id | INT8 | false | NULL | | {bank_address_key,bank_pkey} | false
balance | INT8 | true | NULL | | {bank_pkey} | false
payload | STRING | true | NULL | | {bank_pkey} | false
active | BOOL | true | NULL | | {bank_pkey} | false
location | STRING | true | NULL | | {bank_pkey} | false
currency | STRING | true | NULL | | {bank_pkey} | false
interest | DECIMAL | false | 1.3:::DECIMAL | | {bank_pkey} | false
address | STRING | true | NULL | | {bank_address_key,bank_pkey} | false
cust_number | INT8 | true | NULL | | {bank_pkey} | false
more_names | STRING COLLATE en | true | NULL | | {bank_pkey} | false
(10 rows)
Add a column and assign it to a column family
Add a column and assign it to a new column family
> ALTER TABLE bank ADD COLUMN location1 STRING CREATE FAMILY f1;
> SHOW CREATE TABLE bank;
table_name | create_statement
-------------+--------------------------------------------------------------------------------------------------------------------------------------
bank | CREATE TABLE bank (
| id INT8 NOT NULL,
| balance INT8 NULL,
| payload STRING NULL,
| active BOOL NULL,
| location STRING NULL,
| currency STRING NULL,
| interest DECIMAL NOT NULL DEFAULT 1.3:::DECIMAL,
| address STRING NULL,
| cust_number INT8 NULL,
| more_names STRING COLLATE en NULL,
| location1 STRING NULL,
| CONSTRAINT bank_pkey PRIMARY KEY (id ASC),
| CONSTRAINT fk_cust_number_ref_customers FOREIGN KEY (cust_number) REFERENCES customers(id),
| UNIQUE INDEX bank_address_key (address ASC),
| FAMILY fam_0_id_balance_payload (id, balance, payload, active, location, currency, interest, address, cust_number, more_names),
| FAMILY f1 (location1)
| )
(1 row)
Add a column and assign it to an existing column family
> ALTER TABLE bank ADD COLUMN location2 STRING FAMILY f1;
> SHOW CREATE TABLE bank;
table_name | create_statement
-------------+--------------------------------------------------------------------------------------------------------------------------------------
bank | CREATE TABLE bank (
| id INT8 NOT NULL,
| balance INT8 NULL,
| payload STRING NULL,
| active BOOL NULL,
| location STRING NULL,
| currency STRING NULL,
| interest DECIMAL NOT NULL DEFAULT 1.3:::DECIMAL,
| address STRING NULL,
| cust_number INT8 NULL,
| more_names STRING COLLATE en NULL,
| location1 STRING NULL,
| location2 STRING NULL,
| CONSTRAINT bank_pkey PRIMARY KEY (id ASC),
| CONSTRAINT fk_cust_number_ref_customers FOREIGN KEY (cust_number) REFERENCES customers(id),
| UNIQUE INDEX bank_address_key (address ASC),
| FAMILY fam_0_id_balance_payload (id, balance, payload, active, location, currency, interest, address, cust_number, more_names),
| FAMILY f1 (location1, location2)
| )
(1 row)
Add a column and create a new column family if column family does not exist
> ALTER TABLE bank ADD COLUMN new_name STRING CREATE IF NOT EXISTS FAMILY f2;
> SHOW CREATE TABLE bank;
table_name | create_statement
-------------+--------------------------------------------------------------------------------------------------------------------------------------
bank | CREATE TABLE bank (
| id INT8 NOT NULL,
| balance INT8 NULL,
| payload STRING NULL,
| active BOOL NULL,
| location STRING NULL,
| currency STRING NULL,
| interest DECIMAL NOT NULL DEFAULT 1.3:::DECIMAL,
| address STRING NULL,
| cust_number INT8 NULL,
| more_names STRING COLLATE en NULL,
| location1 STRING NULL,
| location2 STRING NULL,
| new_name STRING NULL,
| CONSTRAINT bank_pkey PRIMARY KEY (id ASC),
| CONSTRAINT fk_cust_number_ref_customers FOREIGN KEY (cust_number) REFERENCES customers(id),
| UNIQUE INDEX bank_address_key (address ASC),
| FAMILY fam_0_id_balance_payload (id, balance, payload, active, location, currency, interest, address, cust_number, more_names),
| FAMILY f1 (location1, location2),
| FAMILY f2 (new_name)
| )
(1 row)
Add a column with an ON UPDATE expression
ON UPDATE expressions set the value for a column when other values in a row are updated.
For example, suppose you add a new column to the bank table:
> ALTER TABLE bank ADD COLUMN last_updated TIMESTAMPTZ DEFAULT now() ON UPDATE now();
> SELECT id, balance, last_updated FROM bank LIMIT 5;
id | balance | last_updated
-----+---------+--------------------------------
0 | 0 | 2021-10-21 17:03:41.213557+00
1 | 0 | 2021-10-21 17:03:41.213557+00
2 | 0 | 2021-10-21 17:03:41.213557+00
3 | 0 | 2021-10-21 17:03:41.213557+00
4 | 0 | 2021-10-21 17:03:41.213557+00
(5 rows)
When any value in any row of the bank table is updated, CockroachDB re-evaluates the ON UPDATE expression and updates the last_updated column with the result.
> UPDATE bank SET balance = 500 WHERE id = 0;
> SELECT id, balance, last_updated FROM bank LIMIT 5;
id | balance | last_updated
-----+---------+--------------------------------
0 | 500 | 2021-10-21 17:06:42.211261+00
1 | 0 | 2021-10-21 17:03:41.213557+00
2 | 0 | 2021-10-21 17:03:41.213557+00
3 | 0 | 2021-10-21 17:03:41.213557+00
4 | 0 | 2021-10-21 17:03:41.213557+00
(5 rows)
See also
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